Backlight Units for Display Devices

ABSTRACT

Embodiments of a device and a method of forming the same are described. The device includes a backlight unit and an image generating unit. The backlight unit includes an optical cavity having a top side, a bottom side, and side walls. The backlight unit further includes an array of light sources coupled to the optical cavity and a quantum dot film positioned within the optical cavity. The quantum dot film is configured to process, light received from the array of light sources and the backlight unit is configured to transit the processed light to the image generating unit. The method includes providing an optical cavity having a top side, a bottom side, and side walls. The method further includes coupling an array of light sources to the optical cavity and supporting a quantum dot film within the optical cavity.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 15/061,115, filed Mar. 4, 2016, which claims the benefit ofU.S. Provisional Patent Application No. 62/273,763, filed Dec. 31, 2015,each of which are hereby incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

Field

The present invention relates to display devices includinglight-emitting diode (LED) based backlight units (BLUs) and phosphorfilms including luminescent nanocrystals such as quantum dots (QDs).

Background

Display devices (e.g., liquid crystal displays (LCDs)) are used asscreens or displays for a wide variety of electronic devices andtypically require some form of backlighting for images to be visible innormal or reduced ambient light environments. In a BLU of the displaydevice, LEDs are typically utilized as a light source. The LEDs may bearranged in a two dimensional array behind the viewing area of thedisplay device or around the edge or perimeter of the display device.The BLU may also utilize phosphors, such as yttrium-aluminum-garnet(YAG) phosphors.

Luminescent nanocrystals represent a new, alternative class of phosphorsoften used in configurations where the phosphor may be placed externalto the LEDs. Light emanating from the LEDs may be processed through aphosphor film of the display device to produce white light, which may bedistributed across a display screen of the display device.

For example, luminescent nanocrystals may be embedded in a flexiblefilm/sheet (e.g., quantum dot enhancement film (QDEF®) suppliedcommercially from 3M Company, St. Paul, Minn. using quantum dotssupplied by Nanosys, Inc, Milpitas, Calif.) that may be placed in thedisplay device (see, e.g., U.S. Patent Publication Nos. 2010/0110728 and2012/0113672, which are incorporated by reference herein in theirentirety). QDEF is a registered trademark of Nanosys, Inc. In otherexamples, luminescent nanocrystals may be encapsulated in a container,for example a capillary (see, e.g., U.S. Patent Publication No.2010/0110728).

In current display devices using QDEFs, the white point values of thelight distributed across display screens depend on the QD populationsize in the QDEFs. The QD population size can be adjusted by changingthe concentration of QDs in the QDEF and/or changing the thickness ofthe QDEF. Furthermore, reducing the QD population size in order toachieve a given white point can reduce the cost of display devices usingQDEF. However, maximum thickness of QDEFs may be limited by thethickness of display devices and maximum QD concentration may be limitedby current technology. These limitations can present challenges inachieving the white point values specified by manufacturers and/orreducing the cost of display devices.

SUMMARY

Disclosed herein are embodiments that overcome the above mentionedlimitations of display devices.

According to an embodiment, a display device includes a BLU and an imagegenerating unit (IGU). The BLU includes an optical cavity having a topside, a bottom side, and side walls. The BLU further includes an arrayof light sources (e.g., LEDs) coupled to the optical cavity and a QDfilm positioned within the optical cavity. The QD film is configured toprocess light received from the array of light sources and the BLU isconfigured to transit the processed light to the image generating unit.

According to an embodiment, the QD film is coupled to a bottom surfaceof the top side.

According to an embodiment, the BLU further includes a first plateconfigured to be optically transmissive and to support the QD filmwithin the optical cavity.

According to an embodiment, the BLU further includes support postsconfigured to support the first plate.

According to an embodiment, the BLU further includes a first plate and asecond plate. The QD film is interposed between the first and secondplates. The first plate is configured to support the QD film.

According to an embodiment, the second plate includes an opticallydiffusive material.

According to an embodiment, the second plate includes an opticallytransparent material and an optically translucent material.

According to an embodiment, the second plate includes an opticallytranslucent material and pores having different sizes in diameter.

According to an embodiment, the QD film includes an array of QD films.

According to an embodiment, each QD film of the array of QD films isconfigured to cover a corresponding row of the array of light sources.

According to an embodiment, the QD film includes an array of QD films.Each QD film of the array of QD films is coupled to a top surface of thebottom side and is configured to enclose a corresponding row of thearray of light sources.

According to an embodiment, the each QD film is configured to form avolume surrounding the corresponding row of the array of light sources.

According to an embodiment, the volume includes a cross-sectional shapeof an arch, a semi-circle, a rectangle, a trapezoid, a triangle, or acombination thereof.

According to an embodiment, the top side of the optical cavity includesan optically diffusive material.

According to an embodiment, the top side of the optical cavity includesan optically transparent material and an optically translucent material.

According to an embodiment, the top side of the optical cavity includesan optically translucent material and pores having different sizes indiameter,

According to an embodiment, the QD film includes a plurality of quantumdots configured to emit red light.

According to an embodiment, the QD film includes a plurality of quantumdots configured to emit green light.

According to an embodiment, the QD film includes a first plurality ofQDs configured to emit red light and a second plurality of QDsconfigured to emit green light.

According to an embodiment, the array of light sources is coupled to atop surface of the bottom side of the optical cavity.

According to an embodiment, the array of light sources includes an arrayof emitting diodes (LEDs).

According to an embodiment, the BLU further includes an opticalprocessing unit having a brightness enhancing film and a polarizing filmcoupled to the brightness enhancing film.

According to an embodiment, the IGU includes a liquid crystal module anda touch screen display coupled to the liquid crystal module.

According to an embodiment, the display device includes at least one ofa liquid crystal display device, a computer, a tablet, a hand-helddevice, a phone, a wearable device, and a TV.

According to an embodiment, a light source unit includes an opticalcavity having a top side, a bottom side, and side walls. The lightsource unit further includes an array of light sources coupled to a topsurface of the bottom side and a QD film positioned between the top sideand the array of light sources. The QD film is configured to processlight received from the array of light sources.

According to an embodiment, the light source unit further includes afirst plate and a second plate. The QD film is interposed between thefirst and second plates. The first plate is configured to support the QDfilm.

According to an embodiment, the QD film includes an array of QD films.

According to an embodiment, each QD film of the array of QD films isconfigured to cover a corresponding row of the array of light sources.

According to an embodiment, the QD film includes an array of QD films.Each QD film of the array of QD films is coupled to a top surface of thebottom side and is configured to enclose a corresponding row of thearray of light sources.

According to an embodiment, the each QD film is configured to form avolume surrounding the corresponding row of the array of light sources.

According to an embodiment, the volume includes a cross-sectional shapeof an arch, a semi-circle, a rectangle, a trapezoid, a triangle, or acombination thereof.

According to an embodiment, a method of forming a display deviceincludes providing an optical cavity having a top side, a bottom side,and side walls. The method further includes coupling an array of lightsources to the optical cavity and supporting a QD film within theoptical cavity.

According to an embodiment, the method further includes providing anoptically diffusive layer as the top side of the optical cavity.

According to an embodiment, the supporting of the QD film includescoupling the QD film to the top side of the optical cavity.

According to an embodiment, the supporting of the QD film includesproviding a first plate positioned within the optical cavity andcoupling the QD film to the first plate.

According to an embodiment, the supporting of the QD film includesproviding a first plate and a second plate positioned within the opticalcavity and interposing the QD film between the first and second plates.

According to an embodiment, the method further includes providing anoptically diffusive layer as the second plate.

According to an embodiment, the method includes coupling the array oflight sources to a top surface of the bottom side of the optical cavity.

According to an embodiment, the method further includes providing anarray of QD films as the QD film.

According to an embodiment, the method further includes providing anarray of QD films as the QD film and forming an enclosed volumesurrounding a corresponding row of the array of light sources using eachQD film of the array of QD films.

According to an embodiment, the forming of the enclosed volume includesbending the each QD film over the corresponding row of the array oflight sources and coupling the each QD film to a top surface of thebottom side of the optical cavity.

Further features and advantages of the invention, as well as thestructure and operation of various embodiments of the invention, aredescribed in detail below with reference to the accompanying drawings.It is noted that the invention is not limited to the specificembodiments described herein. Such embodiments are presented herein forillustrative purposes only. Additional embodiments will be apparent topersons skilled in the relevant art(s) based on the teachings containedherein.

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

The accompanying drawings, which are incorporated herein and form partof the specification, illustrate the present embodiments and, togetherwith the description, further serve to explain the principles of thepresent embodiments and to enable a person skilled in the relevantart(s) to make and use the present embodiments.

FIG. 1 illustrates a schematic of an exploded cross-sectional view adisplay device, according to an embodiment.

FIG. 2 illustrates a schematic of a cross-sectional view of a lightsource unit of a display device, according to another embodiment.

FIG. 3 illustrates a schematic of a cross-sectional view of a lightsource unit of a display device, according to another embodiment.

FIG. 4 illustrates a schematic of a cross-sectional view of a lightsource unit of a display device, according to another embodiment.

The features and advantages of the present invention will become moreapparent from the detailed description set forth below when taken inconjunction with the drawings, in which like reference charactersidentify corresponding elements throughout. In the drawings, likereference numbers generally indicate identical, functionally similar,and/or structurally similar elements. The drawing in which an elementfirst appears is indicated by the leftmost digit(s) in the correspondingreference number. Unless otherwise indicated, the drawings providedthroughout the disclosure should not be interpreted as to-scaledrawings.

DETAILED DESCRIPTION OF THE INVENTION

Although specific configurations and arrangements may be discussed, itshould be understood that this is done for illustrative purposes only. Aperson skilled in the pertinent art will recognize that otherconfigurations and arrangements can be used without departing from thespirit, and scope of the present invention. It will be apparent to aperson skilled in the pertinent art that this invention can also beemployed in a variety of other applications beyond those specificallymentioned herein. It should be appreciated that the particularimplementations shown and described herein are examples and are notintended to otherwise limit the scope of the application in any way.

It is noted that references in the specification to “one embodiment,”“an embodiment,” “an example embodiment,” etc., indicate that theembodiment described may include a particular feature, structure, orcharacteristic, but every embodiment may not necessarily include theparticular feature, structure, or characteristic. Moreover, such phrasesdo not necessarily refer to the same embodiment. Further, when aparticular feature, structure or characteristic is described inconnection with an embodiment, it would be within the knowledge of oneskilled in the art to effect such feature, structure or characteristicin connection with other embodiments whether or not explicitlydescribed.

All numbers in this description indicating amounts, ratios of materials,physical properties of materials, and/or use are to be understood asmodified by the word “about,” except as otherwise explicitly indicated.

In embodiments, the term “display device” refers to an arrangement ofelements that allow for the visible representation of data on a displayscreen. Suitable display screens may include various flat, curved orotherwise-shaped screens, films, sheets or other structures fordisplaying information visually to a user. Display devices describedherein may be included in, for example. display systems encompassing aliquid crystal display (LCD), televisions, computers, mobile phones,smart phones, personal digital assistants (PDAs), gaming devices,electronic reading devices, digital cameras, tablets, wearable devices,car navigation systems, and the like.

The term “about” as used herein includes the recited number ±10%. Thus,“about, ten” means 9 to 11, for example.

In embodiments, the term “optically coupled” means that components arepositioned such that light is able to pass from one component to anothercomponent without substantial interference.

In embodiments, the terms “luminance” and “brightness” are usedinterchangeably and refer to a photometric measure of a luminousintensity per unit area of a light source or an illuminated surface.

In embodiments. the terms “specular reflectors,” “specularly reflectivesurfaces,” and “reflective surfaces” are used herein to refer toelements, materials, and/or surfaces capable of specular reflection.

In embodiments, the term “specular reflection” is used herein to referto a mirror-like reflection of light (or of other kinds of wave) from asurface, when an incident light hits the surface.

In embodiments, the term “white point value” refers to the color whitein terms of a set of chromaticity coordinates, for example, u′ and v′coordinates in CIE 1976 color space, where CIE stands for CommissionInternationale de l'Eclairage (International Commission onIllumination).

In embodiments. the term “unprocessed light” refers to any light thathas not been processed through a phosphor film.

In embodiments, the term “processed light” refers to any light that haspassed through a phosphor film at least once.

The published patents, patent applications, websites, company names, andscientific literature referred to herein are hereby incorporated byreference in their entirety to the same extent as if each wasspecifically and individually indicated to be incorporated by reference.Any conflict between any reference cited herein and the specificteachings of this specification shall be resolved in favor of thelatter. Likewise, any conflict between an art-understood definition of aword or phrase and a definition of the word or phrase as specificallytaught in this specification shall be resolved in favor of the latter.

Technical and scientific terms used herein have the meaning commonlyunderstood by one of skill in the art to which the present applicationpertains, unless otherwise defined. Reference is made herein to variousmethodologies and materials known to those of skill in the art.

Example Embodiment a of Display Device

FIG. 1 illustrates a schematic of an exploded cross-sectional view of adisplay device 100, according to an embodiment. Display device 100 maycomprise a BLU 101 including a light source unit (LSU) 102. BLU 101 mayfurther optionally include an optical processing unit ((SPU) 104.Display device 100 may further include an image generating unit (IGU)106.

LSU 102 may include an optical cavity 110, an array of LEDs 112 (e.g.,white LEDs or blue LEDs) coupled to optical cavity 110, and a phosphorfilm 114. Optical cavity 110 may include a top side 103, a bottom side105, and sidewalls 107 and a closed volume confined by top side 103,bottom side 105, and sidewalls 107. Array of LEDs 112 may be coupled toa top surface 105 a of bottom side 105 within'the closed volume. Arrayof LEDs 112 may be configured to provide a primary light (e.g., a bluelight or a white light) that may be processed through OPU 104 andsubsequently, transmitted to IGU 106 to be distributed across a displayscreen 130 of IOU 106. In some embodiments, array of LEDs 112 may beblue LEDs that emit in the range from about 440 nm to about 470 nm. Insome embodiments, array of LEDs 112 may be white LEDs that emit in therange from about 440 nm to about 700 nm or other possible lightwavelength ranges. In an embodiment, array of LEDs 112 may be atwo-dimensional array of LEDs that are spread across an area of topsurface 105 a and the area may be equal to the surface area of displayscreen 130.

It should be noted that even though two sidewalls 107 are shown in FIG.1, a person skilled in the art would understand that optical cavity 110may include any number of sidewalls 107, according to variousembodiments. For example, optical cavity 110 may have a cuboid shape andmay include four sidewalls similar to sidewalls 107. Optical cavity 110is not restricted to being cuboid in shape or having otherstraight-sided shapes. Optical cavity 110 may be configured to be anytype of geometric shape, such as but not limited to cylindrical,trapezoidal, spherical, or elliptical, according to various embodiments,without departing from the spirit and scope of the present invention. Itshould also be noted that the rectangular cross-sectional shape ofoptical cavity 110, as illustrated in FIG. 1, is for illustrativepurposes, and is not limiting. Optical cavity 110 may have othercross-sectional shapes (e.g., trapezoid, oblong, rhomboid), according tovarious embodiments, without departing from the spirit and scope of thepresent invention.

Top side 103 of optical cavity 110 may be configured to be an opticallydiffusive and transmissive layer such that light from array of LEDs 112after passing through phosphor film 114 may exit optical cavity 110through top side 103. Light exiting optical cavity 110 may have asubstantially uniform distribution of brightness across top surface 103a of top side 103 and may traverse through OPU 104 and/or IGU 106. In anembodiment, top side 103 may include optically transparent areas andoptically translucent areas that are strategically arranged to providethe substantially uniform distribution in light brightness exiting topside 103. In another embodiment, top side 103 may include pores ofvarying sizes in diameters and optically translucent areas that arestrategically arranged to provide the substantially uniform distributionin light brightness exiting top side 103. Top side 103 may includematerials such as, but not limited to, plastic, glass, and/or coatedglass.

Bottom side 105 and/or sidewalls 107 of optical cavity 110 may beconstructed from one or more materials (e.g., metals, non-metals, and/oralloys) that are configured to have scattering, specularly reflective,or a combination thereof top surface 105 a and/or specularly reflectiveside wall interior surfaces 107 a, respectively. In some embodiments,top surface 105 a and/or side wall interior surfaces 107 a may be whitesurfaces having scattering properties, mirror-like surfaces havingmirror-like reflection properties, or a combination thereof. In someembodiments, top surface 105 a and/or side wall interior surfaces 107 amay be completely specularly reflective or partially specularlyreflective and partially scattering. According to some embodiments, topside 103, bottom side 105, and/or sidewalls 107 may be detachablecomponents of optical cavity 110 with respect to each other.

Phosphor film 114 may be a ODEF including luminescent nanocrystals. Inan example embodiment, phosphor film 114 may include a plurality ofphosphors (e.g., luminescent nanocrystals) that emit at the samewavelength, for example. at the wavelength corresponding to green lightor red light in the visible spectrum. In another example embodiment,phosphor film 114 may include a first plurality of phosphors (e.g.,luminescent nanocrystals) that emit at a first wavelength (e.g.,wavelength corresponding to green light) and a second plurality ofphosphors (e.g., luminescent nanocrystals) that emit at a secondwavelength (e.g., wavelength corresponding to red light) that isdifferent from the first wavelength.

Phosphor film 114 may be a down-converter, where at least a portion ofthe primary light from array of LEDs 112 may be absorbed, for example,by QDs in phosphor film 114 and re-emitted as secondary light having alower energy or longer wavelength than the primary light. For example,the first plurality of phosphors and the second plurality of phosphorsmay absorb a portion of the blue light from array of LEDs 112 and beexcited to emit green and red secondary lights, respectively. Theunabsorbed portion of the blue primary light and the emitted green andred secondary lights may be mixed at a predetermined ratio to producewhite light having a desired white point value. The white light mayserve as a backlight of display device 100 after being emitted fromoptical cavity 110, transmitted through IGU 106, and distributed acrossdisplay screen 130, according to an example embodiment.

Phosphor film 114 may be placed within the closed volume of opticalcavity 110. In an embodiment, phosphor film 114 may be coupled to topside 103 using optically transparent adhesive, mechanical fasteners, orany other fastening mechanism such that top surface 114 a of phosphorfilm 114 may be in substantial contact with bottom surface 103 b of topside 103. In another embodiment, phosphor film 114 may be coupled tosidewalls 107 using optically transparent adhesive, mechanicalfasteners, or any other fastening mechanism. The optically transparentadhesive may comprise tape, various glues, polymeric compositions suchas silicones, etc., placed between phosphor film 114 and sidewalls 107and/or bottom surface 103 b. Additional optically transparent adhesivemay include various polymers, including, but not limited to, poly(vinylbutyral), poly(vinyl acetate), epoxies, and urethanes; silicone andderivatives of silicone, including, but not limited to,polyphenylmethylsiloxane, polyphenylalkylsiloxane, polydiphenylsiloxane,polydialkylsiloxane, fluorinated silicones and vinyl and hydridesubstituted silicones; acrylic polymers and copolymers formed frommonomers including, but not limited to, methylmethacrylate,butylmethacryl ate, and laurylmethacrylate; styrene based polymers; andpolymers that are cross linked with difunctional monomers, such asdivinylbenzene, according to various examples.

The position of phosphor film 114 within optical cavity 110, forexample, distance 114 t between array of LEDs 112 and phosphor film 114may depend on thickness 110 t of optical cavity 110 and/or opticaldiffusivity of top side 103. In an example embodiment, distance 114 tmay range from about 20 mm to about 30 mm for a thickness 110 t ofoptical cavity 110 ranging from about 30 mm to about 40 mm.

Placement of phosphor film 114 within optical cavity 110 may allowdisplay device 100 to produce a white point value, of the lightdistributed across display screen 130, substantially similar to thewhite point value of current display devices by using a smaller QDpopulation size in phosphor film 114 than the QD population size inphosphor films placed outside optical cavities in the current displaydevices. For example, display device 100 using about 40% smaller QDpopulation size in phosphor film 114 than the QD population size inphosphor films placed outside optical cavities in the current displaydevices can produce substantially the same white point value as thecurrent display devices.

In an example embodiment, a white point value of about (0.2199, 0.1908)was measured from a display device (e.g., display device 100) having aphosphor film (e.g., phosphor film 114) placed outside an optical cavity(e.g., optical cavity 110) of the display device. The white point valueof the display device shifted to about (0.2728, 0.2609) when thephosphor film was shifted from outside to inside the optical cavity.Such increase in white point value coordinates towards a warmer whitepoint value corresponds to about 50% increase in QD population size inphosphor films placed outside optical cavities in display devices. Inother words, according to some embodiments, substantially similar whitepoint values can be achieved with about 50% smaller QD population sizein phosphor films if the phosphor films are placed inside opticalcavities instead of outside the optical cavities as in current displaydevices.

The ability to reduce QD population size in phosphor films by placingthem within optical cavities to obtain white point values that may becomparable to current, display devices increases the range of whitepoint values that may be achieved in display devices (e.g., displaydevice 100). Such reduction may also help to lower the cost of phosphorfilms in display devices.

Referring to FIG. 1, OPU 104 may be configured to further process thelight received from LSU 102 to desired characteristics for transmissionto IGU 106. OPU 104 may include, but not limited to, a brightnessenhancing film (BEF) 122, a diffuser 124, and a reflective polarizingfilm (RPF) 126. It should be noted that OPU 104 may include more thanone diffuser, BEF, and/or RPF without departing from the spirit andscope of the invention, as would be understood by a skilled person inthe art. Orientations of these elements of OPU 104, their manufactureand incorporation in display devices are known in the art.

BEF 122 may include reflective and/or refractive films, reflectivepolarizer films, prism films, groove films, grooved prism films, prisms,pitches, grooves, or any suitable BEFs or brightness enhancementfeatures known in the art. For example, BEF 122 may include conventionalBEF such as Vikuiti™ or BEF available from 3M™. According to variousembodiments, OPU 104 may include at least one BEF, at least two BEFs, orat least three BEFs. In example embodiments, at least one BEF comprisesa reflective polarizer BEF, e.g., for recycling light which wouldotherwise be absorbed by RPF 126. The brightness-enhancing features andBEF 122 may include reflectors and/or refractors, polarizers, reflectivepolarizers, light extraction features, light recycling features, or anybrightness-enhancing features known in the art. BEF 122 may include afirst layer having pitches or prisms having a first pitch angle,according to an embodiment. Additionally or optionally, another BEF (notshown) in OPU 104 may include a second layer having pitches or prismshaving a second pitch angle that is different from the first pitchangle.

The brightness-enhancing features of BEF 122 may be configured toreflect a portion of the processed light emitting from LSU 102 backtoward phosphor film 114 inside optical cavity 110, thereby providingrecycling of the light back into optical cavity 110. Light transmittedthrough BEF 122 may be dependent on the angle at which the light isincident upon BEF 122. For example, light traveling upward from opticalcavity 110 may transmit through BEF 122 if the light is normal orperpendicular to BEF 122. However, such light may be reflected downwardtoward optical cavity 110 if the light has a higher angle. BEF 122 maybe selected to have multiple reflection angles for light of differentangles to achieve a desired recycling of the processed light from LSU102.

Diffuser 124 is distinct from and supplemental to the scatteringfeatures described herein. According to an example of this embodiment,diffuser 124 may include any diffuser film known in the art, includinggain diffuser films, and may be disposed above or below BEF 122 or otheroptical films of display device 100.

IGU 106 may include an LCD module 128 and display screen 130 and may beconfigured to generate images on display screen 130. Display screen 130may be a touch screen display, according to an example embodiment.

Display device 100 may further comprise one or more medium materials(not shown) disposed between any of the adjacent elements in displaydevice 100, for example between optical cavity 110 and BEF 122; betweenany different layers or regions within OPU 104; between phosphor film114 and array of LEDs 112; and between any other elements of displaydevice 100. The one or more medium materials may include any suitablematerials, including, but not limited to, a vacuum, air, gas, opticalmaterials, adhesives, optical adhesives, glass, polymers, solids,liquids, gels, cured materials, optical coupling materials,index-matching or index-mismatching materials, index-gradient materials,cladding or anti-cladding materials, spacers, epoxy, silica gel,silicones, any matrix materials described herein, brightness-enhancingmaterials, scattering or diffuser materials, reflective oranti-reflective materials, wavelength-selective materials,wavelength-selective anti-reflective materials, color filters, or othersuitable medium material known in the art. Medium materials may alsoinclude optically transparent, non-yellowing, pressure-sensitive opticaladhesives. Suitable materials include silicones, silicone gels, silicagel, epoxies (e.g., Loctite™ Epoxy E-30CL), acrylates (e.g., 3M™Adhesive 2175), and matrix materials mentioned herein. The one or moremedium materials may be applied as a curable gel or liquid and curedduring or after deposition, or pre-formed and pre-cured prior todeposition. Curing methods may include UV curing, thermal curing,chemical curing, or other suitable curing methods known in the art.Index-matching medium materials may be chosen to minimize optical lossesbetween elements of BLU 101.

It should be noted that display device 100 may include components otherthan those discussed herein. Display device 100 may be any type ofgeometric shape, such as but not limited to cylindrical, trapezoidal,spherical, or elliptical, according to various embodiments, withoutdeparting from the spirit and scope of the present invention. Displaydevice 100 is not restricted to being cuboid in shape or having otherstraight-sided shapes. It should also be noted that the rectangularcross-sectional shape of display device 100, as illustrated in FIG. 1,is for illustrative purposes, and is not limiting. Display device 100may have other cross-sectional shapes (e.g., trapezoid, oblong,rhomboid), according to various embodiments, without departing from thespirit and scope of the present invention. It should also be noted thateven though optical cavity 110, BEF 122, diffuser 124, RPF 126, LCDmodule 128, and display screen 130 are shown in FIG. 1 to have similardimensions along X direction, a person skilled in the art wouldunderstand that each of these components may have dimensions differentfrom each other in one or more directions, according to variousembodiments.

Example Embodiments of Light Source Units

FIG. 2 illustrates a schematic of a cross-sectional view of an LSU 202,according to an embodiment. LSU 202 can be implemented as a part ofdisplay device 100, according to an example of this embodiment. LSU 202may be similar to LSU 102 in structure and function except for thedifferences described below.

LSU 202 may include a first plate 216 configured to support phosphorfilm 214 within optical cavity 110. Phosphor film 214 may be similar tophosphor film 114 in structure, composition, and function. Bottomsurface 214 b of phosphor film 214 may be in substantial contact withfirst plate 216. In some embodiments, LSU 202 may further includesupport posts 220.1 and 220.2, mechanical fasteners, and/or any otherfastening mechanism to hold first plate 216 in position within opticalcavity 110. Alternatively, LSU 202 may include a second plate 218positioned on top of phosphor film 214 and coupled to phosphor film 214using optically transparent adhesive, mechanical fasteners, and/or anyother fastening mechanism to hold phosphor film 214 in position withinoptical cavity. Top surface 214 a of phosphor film 214 may be insubstantial contact with second plate 218. Support posts 220.3 and220.4, mechanical fasteners, and/or any other fastening mechanism mayalso be included in LSU 202 to hold second plate 218 in position withinoptical cavity 110. In some embodiments, support posts 220.1 through220.4 may be partially or completely optically transparent. In someembodiments, support posts 220.1 through 220.4 may have scatteringand/or specularly reflective surfaces. It should be noted that therectangular cross-sectional shape of support posts 220.1 through 220.4,as illustrated in FIG. 1, is for illustrative purposes, and is notlimiting. Support posts 220.1 through 220.4 may have othercross-sectional shapes (e.g., triangular, trapezoidal), according tovarious embodiments, without departing from the spirit and scope of thepresent invention.

In an alternate embodiment, LSU 202 may include both first and secondplates 216 and 218 and phosphor film 214 may be interposed between firstand second plates 216 and 218 to form an interposed structure 240. In anembodiment, top and bottom surfaces 214 a and 214 b may be insubstantial contact, with second plate 218 and first plate 216,respectively. In another embodiment, bottom surface 214 b may be insubstantial contact with first plate 216 and a gap (not shown) may existbetween top surface 214 a and second plate 218. Interposed structure 240may be held in position within optical cavity 110 using support posts220.1 through 220.4, optically transparent adhesive, mechanicalfasteners, and/or any other fastening mechanism.

It should be noted that even though four support posts 220.1 through220.4 are shown in FIG. 2, a person skilled in the art would understandthat optical cavity 110 may include any number of support posts,according to various embodiments.

First plate 216 may be configured to be optically transmissive such thatlight from array of LEDs 112 are transmitted to phosphor film 214.Additionally or optionally, first plate 216 may be configured to beoptically diffusive such that substantially uniform distribution oflight from array of LEDs 112 is received across substantially entiresurface area 214 b. Such uniform distribution of light may help toreduce peak light flux received by phosphor film 214 and maximizeperformance, integrity, and lifetime of phosphor film 214.

Second plate 218 may be configured to be optically transmissive anddiffusive such that processed light from phosphor film 214 may passthrough second plate 218 with a substantially uniform distribution ofbrightness across second plate top surface 218 a. In some embodiments,second plate 218 may include optically transparent areas and opticallytranslucent areas or pores of varying sizes in diameters and opticallytranslucent areas that are strategically arranged to provide suchoptically diffusivity in second plate 218.

It should be noted that even though two plates 216 and 218 are shown inFIG. 2, a person skilled in the art would understand that optical cavity110 may include any number of optically transmissive and/or opticallydiffusive plates between phosphor film 214 and array of LEDs 112 andbetween phosphor film 214 and top side 103, according to variousembodiments.

The position of phosphor film 214 within optical cavity 110, forexample, distance 214 t between array of LEDs 112 and phosphor film 214may depend on thickness 110 t of optical cavity 110 and/or opticaldiffusivity of first plate 216, second plate 218, and/or top side 103.Placement of phosphor film 214 within optical cavity 110 may havebenefits similar to the benefits discussed above with respect to theplacement of phosphor film 114 within optical cavity 110.

FIG. 3 illustrates a schematic of a cross-sectional view of an LSU 302,according to an embodiment. LSU 302 can be implemented as a part ofdisplay device 100, according to an embodiment, LSU 302 may be similarto LSUs 102 and 202 in structure and function except for the differencesdescribed below.

LSU 302 may include an array of phosphor films 314 placed within theclosed volume of optical cavity 110. Each of the phosphor films 314 maybe spaced from each other by a gap of 315 along X and/or Y direction.Each of the phosphor films 314 may be similar to phosphor films 114 and214 in composition and function but may be smaller in dimension along,for example, X and/or Y direction compared to phosphor films 114 and214. In an embodiment, each row of array of phosphor films 314 may bearranged to be substantially aligned with a corresponding row of arrayof LEDs 112. In another embodiment, each of the phosphor films 314 mayhave a dimension along Y direction large enough to cover thecorresponding row of array of LEDs 112 along Y direction.

Using array of phosphor films 314, instead of a single phosphor film(e.g., phosphor films 114, 214), to cover an area equal to the surfacearea of a display screen (e.g., display screen 130), may help to reducemanufacturing costs of phosphor films, overcome phosphor film sizelimitations for large display screens, and/or improve production yieldby producing substantially defect-free smaller phosphor films andconsequently, improve yield of display devices.

Array of phosphor films 314 may be supported and held in position withinoptical cavity 110 using top side 103, first plate 216 and/or secondplate 218 and support posts 220.1 through 220.4, optically transparentadhesive, mechanical fasteners, and/or any other fastening mechanism ina manner similar to phosphor films 114 and/or 214 as discussed abovewith reference to FIGS. 1 and 2, respectively.

Similar to phosphor films 114 and 214, the position of array of phosphorfilms 314 within optical cavity 110, for example, distance 3141 betweenarray of LEDs 112 and array of phosphor films 314 may depend onthickness 11011 of optical cavity 110 and/or optical diffusivity offirst plate 216, second plate 218, and/or top side 103.

The position of array of phosphor films 314 within optical cavity 110may also depend on width 315 w of gap 315. In an embodiment, for asubstantially small width 315 w (e.g., width 315 w less than 1 mm),array of phosphor film 314 may be coupled to top side 103 usingoptically transparent adhesive, mechanical fasteners, or any otherfastening mechanism such that top surface 314 a of each of the phosphorfilms 314 may be in substantial contact with bottom surface 103 b.Larger the width 315 w, farther away from top side 103 the array ofphosphor films 314 may be placed within optical cavity 110, and larger avolume 314 v between array of phosphor films 314 and top side 103 may beprovided. Presence of gap 315 may cause light from LEDs to leak throughgap 315 without being processed through array of phosphor films 314 andexit optical cavity 110. The unprocessed light may mix with theprocessed light exiting optical cavity 110 and consequently, adverselyaffect the white point uniformity of a display device (e.g., displaydevice 100). To prevent such an adverse effect, according to anembodiment, volume 314 v may be provided to allow the unprocessed lightto spread out within volume 314 v and lower the intensity of theunprocessed light before exiting optical cavity 110 to a value that maynot adversely affect the white point uniformity of the display device,In an example, array of phosphor films 314 may be placed 10 mm below topside 103 for width 315 w of about 3 mm. Placement of array of phosphorfilms 314 within optical cavity 110 may also have benefits similar tothe benefits discussed above with respect to the placement of phosphorfilms 114 and 214.

FIG. 4 illustrates a schematic of a cross-sectional view of an LSU 402,according to an embodiment. LSU 402 can be implemented as a part ofdisplay device 100, according to an embodiment. LSU 402 may be similarto LSUs 102, 202, and 302 in structure and function except for thedifferences described below.

LSU 402 may include an array of phosphor films 414 placed within theclosed volume of optical cavity 110, Each of the phosphor films 414 maybe similar to phosphor films 114, 214, and 314 in composition andfunction but may be smaller in dimension along, for example, X and/or Ydirection compared to phosphor films 114 and 214. Using array ofphosphor films 414 may have similar benefits as the above mentionedbenefits of using array of phosphor films 314. Placement of array ofphosphor films 414 within optical cavity 110 may also have benefitssimilar to the benefits discussed above with respect to the placement ofphosphor films 114, 214, and 314.

Each of the phosphor films 414 may be bent and coupled to top surface105 a of bottom side 105 using optically transparent adhesive,mechanical fasteners, and/or any other fastening mechanism to form anarray of volumes 419. Volumes 419 may have a cross-sectional shape of anarch, a semi-circle, a triangle, a rectangle, a trapezoid, or any othergeometric shape. It should be noted that even though volumes 419 areshown to have similar cross-sectional shape, each of the volumes 419 mayhave different cross-sectional shapes from each other. Each of thevolumes 419 may enclose a corresponding LED from array of LEDs 112 or acorresponding row of array of LEDs 112 along Y direction. In sucharrangement of phosphor films 414, as discontinuity gaps 415 betweenarray of phosphor films 414 are below emitting surfaces 421 of LEDs 112,leakage of unprocessed light through any discontinuity gaps betweenarray of phosphor films such as discussed above with respect to array ofphosphor films 314 may be minimized or substantially eliminated.

In some embodiments, shape and size of volumes 419 may be optimized toensure substantially uniform distribution of light from LEDs 112 onphosphor films 414 and/or ensure intensity of light from LEDs 112 onphosphor films 414 is within tolerance for temperature and reliability.In some embodiments, emitting surfaces 421 may have lenses coupled tothem. The lenses may have a cylindrical or elliptical symmetry along Xand/or Y direction. In some embodiments, LSU 402 may have plates such asplates 216 and/or 218 placed between tops side 103 and array of phosphorfilms 414.

Example Embodiments of Luminescent Nanocrystal Phosphors

Described herein are various compositions comprising nanocrystals,including luminescent nanocrystals that may be included in phosphorfilms 114, 214, 314, and/or 414 (as described herein with reference toFIGS. 1-4). The various properties of the luminescent nanocrystals,including their absorption properties, emission properties andrefractive index properties, may be tailored and adjusted for variousapplications. As used herein, the term “nanocrystal” refers tonanostructures that are substantially monocrystalline. A nanocrystal mayhave at least one region or characteristic dimension with a dimension ofless than about 500 nm, and down to less than about 1 nm. The terms“nanocrystal,” “nanodot,” “dot,” and “QD” are readily understood by theordinarily skilled artisan to represent like structures and are usedherein interchangeably. The present invention also encompasses the useof polycrystalline or amorphous nanocrystals. As used herein, the term“nanocrystal” also encompasses “luminescent nanocrystals.” As usedherein, the term “luminescent nanocrystals” may mean nanocrystals thatemit light when excited by an external energy source.

The material properties of nanocrystals may be substantially homogenous,or in certain embodiments, may be heterogeneous. The optical propertiesof nanocrystals may be determined by their particle size, chemical orsurface composition. The ability to tailor the luminescent nanocrystalsize in the range between about 1 nm and about 15 nm may enablephotoemission coverage in the entire visible spectrum to offer greatversatility in color rendering. Particle encapsulation may offerrobustness against chemical and UV deteriorating agents.

Nanocrystals, including luminescent nanocrystals, for use in embodimentsdescribed herein may be produced using any method known to those skilledin the art. Suitable methods and example nanocrystals are disclosed inU.S. Pat. No. 7,374,807; U.S. patent application Ser. No. 10/796,832,filed Mar. 10, 2004; U.S. Pat. No. 6,949,206; and U.S. ProvisionalPatent Application No. 60/578,236, filed Jun. 8, 2004, the disclosuresof each of which are incorporated by reference herein in theirentireties.

Luminescent nanocrystals for use in embodiments described herein may beproduced from any suitable material, including an inorganic material,and more suitably an inorganic conductive or semiconductive material.Suitable semiconductor materials may include those disclosed in U.S.patent application Ser. No. 10/796,832, and may include any type ofsemiconductor, including group II-VI, group III-V, group IV-VI and groupIV semiconductors. Suitable semiconductor materials may include, but arenot limited to, Si, Ge, Sn, Se, Te, B, C (including diamond), P, BN, BP,BAs, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, InSb,AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, ZnO, ZnS, ZnSe, ZnTe, CdS,CdSe, CdTe, HgS, HgSe, HgTe, BeS, BeSe, BeTe, MgS, MgSe, GeS, GeSe,GeTe, SuS, SnSe, SnTe, PbO, PbS, PbSe, PbTe, CuF, CuCl, CuBr, CuI,Si₃N₄, Ge₃N₄, Al₂O₃, (Al, Ga, In)₂ (S, Se, Te)₃, Al₂CO, and anappropriate combination of two or more such semiconductors.

In certain embodiments, the nanocrystals may comprise a dopant from thegroup consisting of a p-type dopant or an n-type dopant. Thenanocrystals useful herein may also comprise II-VI or III-Vsemiconductors. Examples of II-VI or III-V semiconductor nanocrystalsmay include any combination of an element from Group II, such as Zn, Cdand Hg, with any element from Group VI, such as S, Se, Te and Po, of thePeriodic Table; and any combination of an element from Group III, suchas B, Al, Ga, In, and Tl, with any element from Group V, such as N, P,As, Sb and Bi, of the Periodic Table.

The nanocrystals, including luminescent nanocrystals, described hereinmay also further comprise ligands conjugated, cooperated, associated orattached to their surface. Suitable ligands may include any group knownto those skilled in the art, including those disclosed in U.S. Pat. No.8,283,412; U.S. Patent Publication No. 2008/0237540; U.S. PatentPublication No. 2010/0110728; U.S. Pat. No. 8,563,133; U.S. Pat. No.7,645,397; U.S. Pat. No. 7,374,807; U.S. Pat. No. 6,949,206; U.S. Pat.No. 7,572,393; and U.S. Pat. No. 7,267,875, the disclosures of each ofwhich are incorporated herein by reference. Use of such ligands mayenhance the ability of the nanocrystals to incorporate into varioussolvents and matrixes, including polymers. Increasing the miscibility(i.e., the ability to be mixed without separation) of the nanocrystalsin various solvents and matrixes may allow them to be distributedthroughout a polymeric composition such that the nanocrystals do notaggregate together and therefore do not scatter light. Such ligands aredescribed as “miscibility-enhancing” ligands herein.

In certain embodiments, compositions comprising nanocrystals distributedor embedded in a matrix material are provided. Suitable matrix materialsmay be any material known to the ordinarily skilled artisan, includingpolymetic materials, organic and inorganic oxides. Compositionsdescribed herein may be layers, encapsulants, coatings, sheets or films.It should be understood that in embodiments described herein wherereference is made to a layer, polymeric layer, matrix, sheet or film,these terms are used interchangeably, and the embodiment so described isnot limited to any one type of composition, but encompasses any matrixmaterial or layer described herein or known in the art.

Down-converting nanocrystals (for example, as disclosed in U.S. Pat. No.7,374,807) utilize the emission properties of luminescent nanocrystalsthat are tailored to absorb light of a particular wavelength and thenemit at a second wavelength, thereby providing enhanced performance andefficiency of active sources (e.g., LEDs).

While any method known to the ordinarily skilled artisan may be used tocreate nanocrystals (luminescent nanocrystals), a solution-phasecolloidal method for controlled growth of inorganic nanomaterialphosphors may be used. See Alivisatos, A. P., “Semiconductor clusters,nanocrystals, and quantum dots,” Science 271:933 (1996); X. Peng. M.Schlamp, A. Kadavanich, A. P. Alivisatos, “Epitaxial growth of highlyluminescent CdSe/CdS Core/Shell nanocrystals with photostability andelectronic accessibility,” J. Am. Chem. Soc. 30:7019-7029 (1997); and C.B. Murray, D. J. Norris, M. G. Bawendi, “Synthesis and characterizationof nearly monodisperse CdE (E=sulfur, selenium, tellurium) semiconductornanocrystallites,”J Am. Chem. Soc. 115:8706 (1993), the disclosures ofwhich are incorporated by reference herein in their entireties. Thismanufacturing process technology leverages low cost processabilitywithout the need for clean rooms and expensive manufacturing equipment.In these methods, metal precursors that may undergo pyrolysis at hightemperature are rapidly injected into a hot solution of organicsurfactant molecules. These precursors may break apart at elevatedtemperatures and react to nucleate nanocrystals. After this initialnucleation phase, a growth phase may begin by the addition of monomersto the growing crystal. The result may be freestanding crystallinenanoparticles in solution that may have an organic surfactant moleculecoating their surface.

Utilizing this approach, synthesis may occur as an initial nucleationevent that takes place over seconds, followed by crystal growth atelevated temperature for several minutes. Parameters such as thetemperature, types of surfactants present, precursor materials, andratios of surfactants to monomers may be modified so as to change thenature and progress of the reaction. The temperature controls thestructural phase of the nucleation event, rate of decomposition ofprecursors, and rate of growth. The organic surfactant molecules maymediate both solubility and control of the nanocrystal shape. The ratioof surfactants to monomer, surfactants to each other, monomers to eachother, and the individual concentrations of monomers may stronglyinfluence the kinetics of growth.

According to an embodiment, CdSe may be used as the nanocrystalmaterial, in one example, for visible light down-conversion, due to therelative maturity of the synthesis of this material. Due to the use of ageneric surface chemistry, it may also possible to substitutenon-cadmium-containing nanocrystals.

In semiconductor nanocrystals, photo-induced emission arises from theband edge states of the nanocrystal. The band-edge emission fromluminescent nanocrystals competes with radiative and non-radiative decaychannels originating from surface electronic states. X. Peng, et al., JAm. Chem. Soc. 30:7019-7029 (1997). As a result, the presence of surfacedefects such as dangling bonds provide non-radiative recombinationcenters and contribute to lowered emission efficiency. An efficient andpermanent method to passivate and remove the surface trap states may beto epitaxially grow an inorganic shell material on the surface of thenanocrystal. X. Peng, et al., J. Am. Chem. Soc. 30:701 9-7029 (1997).The shell material may be chosen such that the electronic levels aretype 1 with respect to the core material (e.g., with a larger bandgap toprovide a potential step localizing the electron and hole to the core).As a result, the probability of non-radiative recombination may bereduced.

Core-shell structures may be obtained by adding organometallicprecursors containing the shell materials to a reaction mixturecontaining the core nanocrystal. In this case, rather than a nucleationevent followed by growth, the cores act as the nuclei, and the shellsmay grow from their surface. The temperature of the reaction is kept lowto favor the addition of shell material monomers to the core surface,while preventing independent nucleation of nanocrystals of the shellmaterials. Surfactants in the reaction mixture are present to direct thecontrolled growth of shell material and to ensure solubility. A uniformand epitaxially grown shell may be obtained when there is a low latticemismatch between the two materials.

Example materials for preparing core-shell luminescent nanocrystals mayinclude, but are not limited to, Si, Ge, Sn, Se, Te, B, C (includingdiamond), P, Co, Au, BN, BP, BAs, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs,GaSb, InN, InP, InAs, InSb, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb,ZnO, ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, HgS, HgSe, HgTc, BeS, BcSe, BcTe,MgS, MgSe, GeS, GeSe, GeTe, SnS, SnSe, SnTe, PbO, PbS, PbSe, PbTe, CuP,CuCl, CuBr, CuI, Si₃N₄, Ge₃N₄, Al₂O₃, (Al, Ga, In)₂ (S, Se, Te)₃, AlCO,and shell luminescent nanocrystals for use in the practice of thepresent invention include, but are not limited to, (represented asCore/Shell), CdSe/ZnS, InP/ZnS, InP/ZnSe, PbSe/PbS, CdSe/CdS, CdTe/CdS,CdTe/ZnS, as well as others.

As used throughout, a plurality of phosphors or a plurality ofluminescent nanocrystals means more than one phosphor or luminescentnanocrystal (i.e., 2, 3, 4, 5, 10, 100, 1,000, 1,000,000, etc.,nanocrystals). The compositions will suitably comprise phosphors orluminescent nanocrystals having the same composition, though in furtherembodiments, the plurality of phosphors or luminescent nanocrystals maybe various different compositions. For example, the luminescentnanocrystals may all emit at the same wavelength, or in furtherembodiments, the compositions may comprise luminescent nanocrystals thatemit at different wavelengths.

Luminescent nanocrystals for use in the embodiments described herein maybe less than about 100 nm in size, and down to less than about 2 nm insize and absorb visible light. As used herein, visible light iselectromagnetic radiation with wavelengths between about 380 and about780 nanometers that is visible to the human eye. Visible light can beseparated into the various colors of the spectrum, such as red, orange,yellow, green, blue, indigo and violet. Blue light may comprise lightbetween about 435 nm and about 500 nm, green light may comprise lightbetween about 520 nm and 565 nm and red light may comprise light betweenabout 625 nm and about 740 nm in wavelength.

According to various embodiments, the luminescent nanocrystals may havea size and a composition such that they absorb photons that are in theultraviolet, near-infrared, and/or infrared spectra. The ultravioletspectrum may comprise light between about 100 nm to about 400 nm, thenear-infrared spectrum may comprise light between about 750 nm to about100 μm in wavelength, and the infrared spectrum may comprise lightbetween about 750 nm to about 300 μm in wavelength.

While luminescent nanocrystals of any suitable material may be used inthe various embodiments described herein, in certain embodiments, thenanocrystals may be. ZnS, InAs, CdSe, or any combination thereof to forma population of nanocrystals for use in the embodiments describedherein. As discussed above, in further embodiments, the luminescentnanocrystals may be core/shell nanocrystals, such as CdSe/ZnS, InP/ZnSe,CdSe/CdS or InP/ZnS.

According to various embodiments, the luminescent nanocrystals mayinclude at least one population of luminescent nanocrystals capable ofemitting red light and/or at least one population of luminescentnanocrystals capable of emitting green light upon excitation by ablue/UV light source. The luminescent nanocrystal wavelengths andconcentrations may be adjusted to meet the optical performance required.In other embodiments, the luminescent nanocrystals phosphor material maycomprise a population of luminescent nanocrystals which absorbwavelengths of light having undesirable emission wavelengths, and reemitsecondary light having a desirable emission wavelength. In this manner,the luminescent nanocrystal films described herein may comprise at leastone population of color-filtering luminescent nanocrystals to furthertune the BLU emission and to reduce or eliminate the need for colorfiltering.

Suitable luminescent nanocrystals, methods of preparing luminescentnanocrystals, including the addition of various solubility-enhancingligands, can be found in Published U.S. Patent Publication No.2012/0113672, the disclosure of which is incorporated by referenceherein in its entirety.

Example Embodiments of Compositions of Phosphors

As used herein, the term “phosphors” refers to a synthetic fluorescentor phosphorescent substance. Example phosphors include traditionalmaterials such as cerium(II)-doped YAG phosphors (YAG:Ce³⁺, orY₃Al₅O₁₂:Ce³⁺), as well as luminescent nanocrystals, as describedherein. Additional phosphors that may be utilized in display devices,such as display device 100, described herein include, but are notlimited to, silicate phosphors, garnet phosphors, aluminate phosphors,nitride phosphors, NYAG phosphors, SiAlON phosphors and CaAlSiN₃-based(CASN) phosphors, as well as other phosphors known in the art.

As described throughout, compositions comprising phosphors for use in,for example, phosphor films 114, 214, 314, and/or 414 (as describedherein with reference to FIGS. 1-4), may have numerous shapes, includingfor example, films'or sheets. In further embodiments, the compositionsmay be various containers or receptacles for receiving the phosphors,suitably luminescent nanocrystals.

Suitably, phosphors, and specifically luminescent nanocrystals, may bedispersed or embedded in suitable polymeric materials and sandwichedbetween one or more barrier layers on either side of the matrix tocreate films or sheets, such as phosphor films 114, 214, 314, and/or414, also called quantum dot enhancement films (QDEFs). Such films aredescribed, for example, in U.S. Patent Publication Nos. 2010/0110728 and2012/0113672, the disclosures of each of which are incorporated byreference herein in their entireties.

The luminescent nanocrystals of phosphor films 114, 214, 314, and/or 414may be coated with one or more ligand coatings, embedded in one or morefilms or sheets, and/or sealed by one or more barrier layers. Suchligands, films, and barriers may provide photostability to theluminescent nanocrystals and protect the luminescent nanocrystals fromenvironmental conditions including elevated temperatures, high intensitylight, external gases, moisture, and other harmful environmentalconditions. Additional effects may be achieved with these materials,including a desired index of refraction in the host film material, adesired viscosity or luminescent nanocrystal dispersion/miscibility inthe host film material, and other desired effects. In embodiments, theligand and film materials will be chosen to have a sufficiently lowthermal expansion coefficient, such that thermal curing does notsubstantially affect the luminescent nanocrystal phosphor material.

The luminescent nanocrystals of phosphor films 114, 214, 314, and/or 414may comprise ligands conjugated to, cooperated with, associated with, orattached to their surface. In an embodiment, the luminescentnanocrystals may include a coating layer comprising ligands to protectthe luminescent nanocrystals from external moisture and oxidation,control aggregation, and allow for dispersion of the luminescentnanocrystals in the matrix material. Ligands and matrix materials, aswell as methods for providing such materials, are described herein.Additional ligands and film materials, as well as methods for providingsuch materials, include any group known to those skilled in the art,including those disclosed in U.S. Patent Publication No. 2012/0113672;U.S. Pat. No. 8,283,412; U.S. Patent Publication No. 2008/0237540; U.S.Patent Publication No. 2010/0110728; U.S. Pat. No. 8,563.133; U.S. Pat.No. 7,645,397; U.S. Pat. No. 7,374,807; U.S. Pat. No. 6,949,206; U.S.Pat. No. 7,572,393; and U.S. Pat. No. 7,267,875, the disclosure of eachof which is incorporated herein by reference in its entirety.Additionally, ligand and matrix materials may include any suitablematerials in the art.

Dispersing luminescent nanocrystals in a polymeric material provides amethod to seal the nanocrystals and provide a mechanism for mixingvarious compositions and sizes of luminescent nanocrystals. As usedthroughout, “dispersed” includes uniform (i.e., substantiallyhomogeneous) as well as non-uniform (i.e., substantially heterogeneous)distribution or placement of luminescent nanocrystals.

Materials for use in the compositions (e.g., phosphor films 114, 214,314, and/or 414) comprising the luminescent nanocrystals may includepolymers and organic and inorganic oxides. Polymers may include anypolymer known to the ordinarily skilled artisan that may be used forsuch a purpose. In an embodiment, the polymer may be substantiallytranslucent or substantially transparent. Matrix materials may include,but are not limited to, epoxies; acrylates; norborene; polyethylene;polyvinyl butyral):poly(vinyl acetate); polyurea; polyurethanes;silicones and silicone derivatives including, but not limited to, aminosilicone (AMS), polyphenylmethylsiloxane, polyphenylalkylsiloxane,polydiphenylsiloxane, polydialkylsiloxane, silsesquioxanes, fluorinatedsilicones, and vinyl and hydride substituted silicones; acrylic polymersand copolymers formed from monomers including, but not limited to,methylmethacrylate, butylmethacrylate, and laurylmethacrylate;styrene-based polymers such as polystyrene, amino polystyrene (APS), andpolyacrylonitrile ethylene styrene) (AES); polymers that are crosslinkedwith difunctional monomers, such as divinylbenzene; cross-linkerssuitable for cross-linking ligand materials; epoxides which combine withligand amines (e.g., APS or PEI ligand amines) to form epoxy, and thelike.

The luminescent nanocrystals as described herein may be embedded in apolymeric (or other suitable material, e.g., waxes, oils) matrix usingany suitable method, for example, mixing the luminescent nanocrystals ina polymer and casting a film; mixing the luminescent nanocrystals withmonomers and polymerizing them together; mixing the luminescentnanocrystals in a sol-gel, or any other method known to those skilled inthe art. As used herein, the term “embedded” is used to indicate thatthe luminescent nanocrystals are enclosed or encased within the polymer.It should be noted that luminescent nanocrystals may be uniformlydistributed throughout the composition, though in further embodimentsthey may be distributed according to an application-specific uniformitydistribution function.

The thickness of the compositions (e.g., phosphor films 114, 214, 314,and/or 414) comprising luminescent nanocrystals as described herein maybe controlled by any method known in the art, such as spin coating andscreen printing. The luminescent nanocrystal compositions (e.g.,phosphor films 114, 214, 314, and/or 414) as described herein may be anydesirable size, shape, configuration and thickness. For example, thecompositions (e.g., phosphor films 114, 214, 314, and/or 414) may be inthe form of layers, as well as other shapes, for example, discs,spheres, cubes or blocks, tubular configurations and the like. Thecompositions (e.g., phosphor films 114, 214, 314, and/or 414) are on theorder of about 100 μm in thickness i.e., in one dimension. In otherembodiments, the polymeric films may be on the order of 10's to 100's ofmicrons in thickness. The luminescent nanocrystals may be embedded inthe various compositions at any loading ratio that is appropriate forthe desired function. For example, the luminescent nanocrystals may beloaded at a ratio of between about 0.001% and about 75% by volumedepending upon the application, polymer and type of nanocrystals used.The appropriate loading ratios can readily be determined by theordinarily skilled artisan and are described herein further with regardto specific applications. In an embodiment, the amount of nanocrystalsloaded in a luminescent nanocrystal composition (e.g., in phosphor films114, 214, 314, and/or 414) may be on the order of about 10% by volume,to parts-per-million (ppm) levels.

It is to be understood that while certain embodiments have beenillustrated and described herein, the claims are not to be limited tothe specific forms or arrangement of parts described and shown. In thespecification, there have been disclosed illustrative embodiments and,although specific terms are employed, they are used in a generic anddescriptive sense only and not for purposes of limitation. Modificationsand variations of the embodiments are possible in light of the aboveteachings. It is therefore to be understood that the embodiments may bepracticed otherwise than as specifically described.

1. A method of forming a display device, the method comprising: providing an optical cavity having a top side, a bottom side, and side walls; coupling an array of light sources to the, optical cavity; and supporting a quantum dot (QD) film within the optical cavity.
 2. The method of claim 1, further comprising providing an optically diffusive layer as the top side of the optical cavity.
 3. The method of claim 1, wherein the supporting of the QD film comprises coupling the QD film to the top side of the optical cavity.
 4. The method of claim 1, wherein the supporting of the QD film comprises: providing a first plate positioned within the optical cavity; and coupling, the QD film to the first plate.
 5. The method of claim 1, wherein the supporting of the QD film comprises: providing a first plate and a second plate positioned within the optical cavity; and interposing the QD film between the first and second plates.
 6. The method of claim 5, further comprising providing an optically diffusive layer as the second plate.
 7. The method of any one of claims 1, comprising coupling the array of light sources to a top surface of the bottom side of the optical cavity.
 8. The method of any one of claims 1, further comprising providing an array of QD films as the QD film.
 9. The method of claim 1, further comprising: providing an array of QD films as the QD film; and forming an enclosed volume surrounding a corresponding, row of the array of light sources using each QD film of the array of QD films.
 10. The method of claim 9, wherein the forming of the enclosed comprises: bending the each QD film over the corresponding row of the array of light sources; and coupling the each QD film to a top surface of the bottom side of the optical cavity.
 11. A method comprising: providing an optical cavity having a top side, a bottom side, and side walls; coupling an array of light sources to the optical cavity; and supporting an array of quantum dot (QD) films within the optical cavity.
 12. The method of claim 11, wherein the supporting of the array of QD films comprises coupling the array of QD films to a top side of the optical cavity.
 13. The method of claim 11, wherein the supporting of the array of QD films comprises: providing a first plate positioned within the optical cavity; and coupling the array of QD films to the first plate.
 14. The method of claim 11, further comprising forming an enclosed volume surrounding a corresponding row of the array of light sources using each QD film of the array of QD films.
 15. A method of forming a light source unit, the method comprising: providing an optical cavity; coupling an array of light sources to a bottom side of the optical cavity; and coupling an array of quantum dot (QD) films within the optical cavity.
 16. The method of claim 15, further comprising forming an enclosed volume surrounding a corresponding row of the array of light sources using each QD film of the array of QD films.
 17. The method of claim 16, wherein the forming of the enclosed volume comprises bending the each QD film over the corresponding row of the array of light sources. 